Compression/coding techniques are often used in transmitting speech/sound signals in a packet communication system typified by internet communication, and a mobile communication system, for the purpose of improving the transmission efficiency of speech/sound signals. In recent years, a need for a coding technique involving processing with a low amount of computation or a multi-rate coding technology rather than simply encoding speech/audio signals at low bit rate has been increasing.
To meet this need, various techniques for encoding speech/sound signals with a low amount of computation without significantly increasing the amount of information after coding have been developed. Non-Patent Literature 1, for example, discloses a technique that divides spectrum data acquired by transforming input signals in a predetermined time, into a plurality of sub-vectors and performs multi-rate coding for each sub-vector. Non-Patent Literature 2, Non-Patent Literature 3, and Patent Literature 1 also disclose a technique related to EAVQ (Embedded Algebraic Vector Quantization) disclosed in the above Non-Patent Literature 1.